/*程序2-5c：圆周率用const常量*/
#include <stdio.h>
#define PI 3.1415926
// //求圆柱体的体积(volume)
int main(void) {
    double r = 10.0;
    double h = 20.0;
    double v = PI * r * r * h;
    printf("v=%f\n", v);
    return 0;
}
